Development of 120KV Electron Microscope

Abstract

A new electron microscope (EM) of 120 kV has been developed. This EM is designed for biological study but it incorporates many new ideas as a new transmission electron microscope. The main features of this new electron microscope are as follows.A. New Lens System and ControlThe illumination lens and imaging lens system and these control methods have been improved in this EM. It has three illumination mode, which are the spot focus mode, the parallel focus mode and the α focus mode. In the parallel focus mode, the cross over point under the specimen is kept on an objective aperture, which is placed in the back focal plane. That makes it possible to set the small objective aperture such as 20 micron without field cut and any sacrifices of specimen tilting angle at very low magnification. The objective lens condition in the diffraction mode is depending on the imaging mode, which are MAG mode and LOW MAG mode. That means it has two diffraction mode, the objective lens is kept on in one mode and off in the other mode corresponding to the imaging mode, MAG and LOW MAG modes. So the beam position is kept exactly on the specified area on the specimen during the changeover between the imaging mode and diffraction mode.